Optical fiber measuring module

ABSTRACT

An optical fiber measuring module is provided with an optical fiber cable ( 2 ) including an optical fiber core ( 2   a ), a cladding ( 2   b ) and a covering layer ( 2   c ), a base member ( 3 ) for holding the optical fiber cable ( 2 ), and an attachment member ( 4 ) for attaching the base member ( 3 ) to a structure ( 1 ).

FIELD OF TECHNOLOGY

The present invention relates to an optical fiber measuring module whichis laid on a structure such as a bridge, a tunnel or a building tomeasure the distortion, the temperature or other physical quantity ofthe structure.

TECHNOLOGICAL BACKGROUND

In recent years, there have been developed various optical fibermeasuring modules for measuring the distortion, the temperature or otherphysical quantity of a structure such as a bridge, a tunnel or abuilding using characteristics of an optical fiber.

This optical fiber measuring module generally includes an optical fibercore, a cladding, and a covering layer and is adapted to measure thedistortion, the temperature or other physical quantity of the opticalfiber core by causing a discontinuous pump light such as a laser beam tobe incident on the optical fiber core to create a scattered lightresulting from the distortion, the temperature and the like of theoptical fiber core such as Brillouin scattering or Raman scattering andby detecting the scattered light. Since this optical fiber measuringmodule can measure a physical quantity at an arbitrary position alongthe longitudinal direction of the optical fiber core by controlling asampling timing for detecting the scattered light, it is used for theremote measurement of a distortion, a temperature and the like at anarbitrary position of a structure. Various related technologies havebeen and are being developed.

For example, Japanese Unexamined Patent Publication No. H09-14927discloses a technology concerning an optical fiber sensor comprised of ametal tube and a spiral optical fiber held in contact with the innercircumferential surface of the metal tube, and a method for measuringthe distortion of a structure using such an optical fiber sensor.

Further, Japanese Unexamined Patent Publication No. 2002-131025discloses a technology concerning a surface distortion sensor formeasuring the distortion of a concrete structure to confirm the progressof a damage of the concrete structure by holding one or more opticalfiber cables between sheet-shaped materials through which an adhesive ispermeable to fix the optical fiber cables and adhering the resultingsheet to an outer surface of the concrete structure using the adhesive.

However, with the technologies of the above optical fiber measuringmodule, there are problems of difficulty to rebuild an optical fiber netonce this net is cut, and likeliness to damage the optical fiber corerequired to be carefully handled upon attachment or detachment.

For example, in the case of the technology disclosed in JapaneseUnexamined Patent Publication No. H09-14927, it is not easy to attachthe metal tube provided with the optical fiber to the structure whilealigning it with the structure and the optical fiber core may be damagedif bending or other working is applied to the metal tube.

In the case of the technology disclosed in Japanese Unexamined PatentPublication No. 2002-131025 as well, there are not only a problem thatit is not easy to attach and detach the optical fiber measuring module,but also a problem that an excessive load acts on the optical fibercable upon peeling off the adhered sheet and the optical fiber cores arelikely to be damaged since the sheet-shaped optical fiber measuringmodule is adhered to the outer surface of the concrete structure usingthe adhesive.

In view of the above problems, an object of the present invention is toprovide an optical fiber measuring module which can be easily attachedto and detached from a structure, and is free from damaging an opticalfiber core required to be carefully handled upon attachment anddetachment.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an optical fibermeasuring module is to be laid on a structure for measuring at least onephysical quantity from the distortion and temperature of the structure.The optical fiber measuring module is provided with an optical fibercable including an optical fiber core, a cladding and a covering layer.The module is further provided with a base member for holding theoptical fiber cable, and an attachment member for attaching the basemember to the structure.

These and other objects, features, aspects, and advantages of thepresent invention will become more apparent from the following detaileddescription of the preferred embodiments/examples with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a construction of an optical fibermeasuring module according to a first embodiment of the invention.

FIG. 2 is a perspective view showing the attachment of the optical fibermeasuring module according to the first embodiment of the invention to astructure.

FIG. 3 is a perspective view showing a construction of an optical fibermeasuring module according to a second embodiment of the invention.

FIGS. 4A and 4B are sections showing a modification of a locking deviceof the optical fiber measuring module according to the second embodimentof the invention, wherein FIG. 4A shows a state where a base member isattached to an attachment member by the locking device and FIG. 4B showsan intermediate state during the detachment of the base member from theattachment member.

FIGS. 5A, 5B and 5C are diagrams showing a construction of an opticalfiber measuring module according to a third embodiment of the invention,wherein FIG. 5A is a plan view showing the construction of the opticalfiber measuring module according to the third embodiment, FIG. 5B is aside view of an attachment member, and FIG. 5C is a graph showing theintensity of a distortion acting on an optical fiber cable after thebase member is attached to the attachment member.

FIG. 6 is a perspective view showing a construction of an optical fibermeasuring module according to a fourth embodiment of the invention.

FIGS. 7A and 7B are diagrams showing a construction of an optical fibermeasuring module according to a fifth embodiment of the invention,wherein FIG. 7A is a perspective view of the optical fiber measuringmodule and FIG. 7B is a table showing effects of the optical fibermeasuring module.

FIG. 8 is a perspective view showing a construction of an optical fibermeasuring module according to a sixth embodiment of the invention.

FIG. 9 is a perspective view showing a construction of an optical fibermeasuring module according to a seventh embodiment of the invention.

FIG. 10 is a perspective view showing a construction of an optical fibermeasuring module according to an eighth embodiment of the invention.

FIG. 11 is a section showing the action of the optical fiber measuringmodule according to the eight embodiment of the invention.

FIG. 12 is a perspective view showing a construction of an optical fibermeasuring module according to a ninth embodiment of the invention.

FIG. 13 is a perspective view showing a construction of an optical fibermeasuring module according to a tenth embodiment of the invention.

FIG. 14 is a perspective view showing a construction of an optical fibermeasuring module according to an eleventh embodiment of the invention.

FIG. 15 is a perspective view showing a construction of a unit of theoptical fiber measuring module according to the eleventh embodiment ofthe invention.

FIG. 16 is a perspective view showing a construction of a polarizingring of the optical fiber measuring module according to the eleventhembodiment of the invention.

FIGS. 17A and 17B are side views showing a construction of a loadingmechanism of the polarizing ring, wherein FIG. 17A shows a state wherethe length of a discontinuous portion is not changed by a loading memberand FIG. 17B shows a state where the length of the discontinuous portionis changed by the loading member.

FIGS. 18A and 18B show a modification of the base member, wherein FIG.18A is a perspective view of the modification of the base member andFIG. 18B is a graph of a distortion of the optical fiber cable showingan effect of the modification of the base member.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention aredescribed in detail with reference to the accompanying drawings. FIG. 1is a perspective view showing a construction of an optical fibermeasuring module according to a first embodiment of the invention, andFIG. 2 is a perspective view showing the attachment of the optical fibermeasuring module according to the first embodiment of the invention to astructure.

With reference to FIGS. 1 and 2, a shown optical fiber measuring module10 according to the first embodiment of the present invention measuresat least one physical quantity of the distortion and the temperature ofthe structure 1 by laying an optical fiber cable 2 on a structure 1. Inorder to enable the optical fiber measuring module 10 to be attached tothe structure 1 without influencing the optical fiber cable 2 whichrequires a careful attention, a base member 3 for holding the opticalfiber cable 2 and an attachment member 4 for attaching this base member3 to the structure 1 are provided.

In order to attach the attachment member 4 to the structure 1 withoutworking the structure 1 and the attachment member 4 every time, anattaching device 5 is provided between the attachment member 4 and thestructure 1, so that the attachment member 4 can be easily attached tothe structure 1. In order to enable the optical fiber measuring module10 to be attached to the structure 1 by successively locking the basemember in the attachment member 4 with the attachment member 4 attachedto the structure 1, a locking device 6 is provided between the basemember 3 and the attachment member 4, so that the base member 3 can beeasily locked in the attachment member 4.

The optical fiber cable 2 is adapted to measure the distortion, thetemperature and other physical quantity of the optical fiber cable 2 bycausing a discontinuous pump light such as a laser beam to be incidentthereon to create a scattered light resulting from the distortion, thetemperature and the like of the optical fiber cable such as Brillouinscattering or Raman scattering and by detecting the scattered light. Theoptical fiber cable 2 includes an optical fiber core 2 a, a cladding 2b, and a covering layer 2 c.

The base member 3 is for holding the optical fiber cable 2, made of aplate material having a certain degree of flexibility such as a metallicthin plate or a synthetic resin plate, and so formed as to be attachableto structures 1 of various shapes via the attachment member 4.

The attachment member 4 is provided to attach the base member 3 to thestructure 1. Likewise, the attachment member 4 is made of a platematerial having a certain degree of flexibility such as a metallic thinplate or a synthetic resin plate and so formed as to be attachable tostructures 1 of various shapes via the attachment member 4.

The attaching device 5 includes an adhering layer 7 provided on theattachment member 4 and made of an adhesive or a welding agent foradhering the attachment member 4 and the structure 1 in the firstembodiment in order to enable the attachment member 4 to be attached tothe structure 1 without damaging the optical fiber cable 2. Thus, theattachment member 4 can be attached to the structure 1 withoutconsidering the optical fiber cable 2.

The locking device 6 is constructed such that a locking portion 6 aprovided in the attachment member 4 is engaged with an engaging portion6 b of the base member 6 b to lock the base member 3 in the attachmentmember 4 in order to enable the base member to be attached to theattachment member 4 in one operation without requiring any part forattachment such as screws.

The functions of the optical fiber measuring module 10 according to thefirst embodiment are described. Since this optical fiber measuringmodule 10 is provided with the base member 3 for holding the opticalfiber cable 2, the base member 3 can be handled upon handling theoptical fiber measuring module and the optical fiber cable 2 requiring acareful attention need not be directly handled. Further, since theattachment member 4 for attaching the base member 3 to the structure 1is provided, the optical fiber measuring module 1 can be easily attachedwithout influencing the optical fiber cable 2.

Since the attaching device 5 for attaching the attachment member 4 tothe structure 1 is provided between the attachment member 4 and thestructure 1 in the optical fiber measuring module 10, the attachmentmember 4 can be easily attached to the structure 1 every time.

Further, since the locking device 6 for locking the base member 3 in theattachment member 4 is provided between the base member 3 and theattachment member 4, the optical fiber measuring module 1 can be easilyattached to the structure 1 by successively locking the base member 3 inthe attachment member 4 with the attachment member 4 attached to thestructure 1.

Particularly, in this optical fiber measuring module 10, the attachmentmember 4 is attached to the structure 1 by means of the attaching device5 provided at the attachment member 4 and including the adhering layer 7made of an adhesive or welding agent for adhering the attachment member4 and the structure 1. Thus, the attachment member 4 can be easilyattached to the structure 1 in one operation without requiring any partfor attachment such as screws.

Furthermore, since the base member 3 is locked in the attachment member4 by the locking device 6 for engaging the locking portion 6 a providedin the attachment member 4 with the engaging portion 6 b provided on thebase member 3 in this optical fiber measuring module 10, the base member3 can be easily attached to the attachment member 4 in one operationwithout requiring any part for attachment such as screws.

Next, a second embodiment of the present invention is described withreference to FIG. 3. FIG. 3 is a perspective view showing a constructionof an optical fiber measuring module 20 according to the secondembodiment of the invention.

With reference to FIG. 3, in the optical fiber measuring module 20 ofthe second embodiment, the attaching device 5 includes a bottomedlocking groove 5 c formed in the structure 1 and narrower at an opening5 a than at a bottom portion 5 b, an engaging projection 5 d provided onthe attachment member 4 and engageable with the locking groove 5 c and aresilient sheet 5 e made of a resilient member in order to enable theattachment member 4 to be easily attached to the structure 1 in oneoperation. The attachment member 4 is attached to the structure 1 bypushing the engaging projection 5 d into the locking groove 5 c via theresilient sheet 5 e.

The functions of the optical fiber measuring module 20 according to thesecond embodiment are described. Since the attachment member 4 can beattached to the structure 1 by the attaching device 5 of pushing theengaging projection 5 d provided on the attachment member 4 into thebottomed locking groove 5 c via the resilient sheet 5 e in this opticalfiber measuring module 20, the attachment member 4 can be easilyattached to the structure 1 in one operation without requiring any partfor attachment such as screws.

Further, since the base member 3 is locked in the attachment member 4 bythe locking device 6 of engaging the locking portion 6 a provided in theattachment member 4 with the engaging portion 6 b provided on the basemember 3 in this optical fiber measuring module 20, the base member 3can be easily attached to the attachment member 4 in one operationwithout requiring any part for attachment such as screws.

FIGS. 4A and 4B show a modification of the locking device 6 of theoptical fiber measuring module according to the second embodiment of thepresent invention, wherein FIG. 4A shows a state where the base member 3is attached to the attachment member 4 by the locking device 6 and FIG.4B shows an intermediate state during the detachment of the base member3 from the attachment member 4.

With reference to FIGS. 4A and 4B, in this modification, the lockingdevice 6 has a zipper structure in which locking portions 6 a providedon the attachment member 4 are formed into hooks and engaging portions 6a provided on the attachment member 4 are formed into hooks engageablewith the hooked locking portions 6 a in order to enable the base member3 to be attached to the attachment member 4 in one operation. By takingthe zipper structure, the locking device 6 of this modification candetachably lock the base member 3 in the attachment member 4 bysuccessively engaging the locking device 6 from one end thereof.

The functions of the locking device 6 according to this modification aredescribed. In this modification, by the locking device 6 having such azipper structure as to engage the hooked engaging portions 6 b providedon the base member 3 with the hooked locking portions 6 a provided onthe attachment member 3, the base member 3 is detachably locked in theattachment member 4 by successively engaging the engaging portions 6 bwith the locking portions 6 a from one end of the locking device 6.Thus, the base member 3 can be fairly easily attached to the attachmentmember 4.

Since the locking device 6 has the zipper structure as above, theengaging portions 6 b can be successively engaged with and disengagedfrom the locking portions 6 a from one end of the locking device 6. As aresult, the base member 3 can be detachably attached to the attachmentmember 4 in one operation.

Next, a third embodiment of the present invention is described withreference to FIGS. 5A to 5C. FIGS. 5A, 5B and 5C are diagrams showing aconstruction of an optical fiber measuring module 30 according to thethird embodiment of the invention, wherein FIG. 5A is a plan viewshowing the construction of the optical fiber measuring module 30according to the third embodiment, FIG. 5B is a side view of theattachment member 4, and FIG. 5C is a graph showing the intensity of adistortion acting on the optical fiber cable 2 after the base member 3is attached to the attachment member 4.

With reference to FIGS. 5A to 5C, in the optical fiber measuring module30 of the third embodiment, the locking device 6 is constructed suchthat intervals S1, S2 between the locking portions 6 a provided on theattachment member 4 and intervals S3 between the engaging portions 6 bprovided in the attachment member 4 are differed to give a distortion tothe base member 3 locked in the attachment member 4 to elongate orcontract the base member 3, thereby setting an initial distortion of theoptical fiber cable 2.

The functions of the optical fiber measuring module 30 according to thefirst embodiment are described. In this optical fiber measuring module30, since a distortion can be given to the base member 3 locked in theattachment member 4 to elongate or contract the base member 3 bydiffering the intervals S1, S2 between the locking portions 6 a providedon the attachment member 4 and the intervals S3 between the engagingportions 6 b provided in the base member 3, the initial distortion ofthe optical fiber cable 2 can be set. As a result, a measurement rangeof the optical fiber measuring module 30 can be properly set.

Next, a fourth embodiment of the present invention is described withreference to FIG. 6. FIG. 6 is a perspective view showing a constructionof an optical fiber measuring module 40 according to the fourthembodiment of the invention.

With reference to FIG. 6, in the optical fiber measuring module 40 ofthe fourth embodiment, the base member 3 holds two optical fiber cables2 at a specified distance from each other, whereby at least one statequantity of the elongation, bending, and partial lateral pressure of thestructure on which the optical fiber measuring module is laid can bemeasured from measurement values of the distortions of the two opticalfiber cables 2 and increasing/decreasing patterns of the measurementvalues.

Particularly in the fourth embodiment, the base member 3 is strip-shapedand so constructed as to hold the two optical fiber cables 2 along thelongitudinal direction of the base member 3 at a specified distance fromeach other in order to enable the efficient measurement of statequantities of the structure 1 such as the planar deformation anddistortion thereof in a remote place by a simple construction.

The functions of the optical fiber measuring module 40 according to thefourth embodiment are described. Since the base member 3 holds the twooptical fiber cables 2 d, 2 e at a specified distance from each other inthis optical fiber measuring module 40, at least one state quantity ofthe elongation, bending, and partial lateral pressure of the structureon which the optical fiber measuring module is laid can be measured fromthe measurement values of the distortions of the two optical fibercables 2 and the increasing/decreasing patterns of the measurementvalues. As a result, the state quantities of the structure 1 such as thedeformation and distortion thereof can be efficiently measured in aremote place.

Particularly in this embodiment, the two optical fiber cables 2 d, 2 eare held along the longitudinal direction of the strip-shaped basemember 3 at the specified distance from each other. Thus, the statequantities of the structure 1 such as the planar deformation anddistortion thereof can be efficiently measured in a remote place by thesimple construction.

Next, a fifth embodiment of the present invention is described withreference to FIGS. 7A and 7B. FIGS. 7A and 7B are diagrams showing aconstruction of an optical fiber measuring module 50 according to thefifth embodiment of the invention, wherein FIG. 7A is a perspective viewof the optical fiber measuring module 50 and FIG. 7B is a table showingeffects of the optical fiber measuring module 50.

With reference to FIG. 7A, in the optical fiber measuring module 50 ofthe fifth embodiment, the base member 3 includes a strip-shaped flatportion 3 a and a wall portion 3 b standing substantially uprightsubstantially in the middle of the flat portion 3 a, two optical fibercables 2 d, 2 e are held along the longitudinal direction of the flatportion 3 a at a specified distance from each other, and another opticalfiber 2 f is held along the longitudinal direction of the wall portion 3b.

The functions of the optical fiber measuring module 50 according to thefifth embodiment are described. In this optical fiber measuring module50, the two optical fibers cables 2 d, 2 e are held along thelongitudinal direction of the strip-shaped flat portion 3 a at thespecified distance from each other, and one more optical fiber cable 2 fis held along the longitudinal direction of the wall portion 3 bstanding substantially upright, thereby three-dimensionally arrangingthe optical fiber cables 2. Thus, state quantities of the structure 1such as the planar deformation and distortion thereof can be efficientlymeasured in a remote place by a simple construction.

Particularly, with reference to FIG. 7B, in this optical fiber measuringmodule 50, the elongative distortions of the fiber cables 2 d, 2 e and 2f are respectively observed as (+) if an elongation of x-axis acts onthe center axis of the base member 3; only the elongative distortion ofthe fiber cable 2 f is observed as (+) if a lateral pressure acts on aportion C in z-axis direction; and the elongative distortion of thefiber cable 2 d is observed as (+) while that of the fiber cable 2 e isobserved as (−) if a bending force acts about z-axis. Thus, the cause ofthe distortion such as the elongation along the center axis of the basemember 3, the action of the lateral pressure or the action of thebending force can be analyzed by analyzing such a distortion pattern ofthe fiber cables 2 d, 2 e, 2 f.

Next, a sixth embodiment of the present invention is described withreference to FIG. 8. FIG. 8 is a perspective view showing a constructionof an optical fiber measuring module 60 according to the sixthembodiment of the invention.

With reference to FIG. 8, in the optical fiber measuring module 60 ofthe sixth embodiment, the base member 3 is formed into a tube in orderto enable measurements of state quantities such as the three-dimensionaldeformation and distortion of the structure 1, and three optical fibercables 2 d, 2 e, 2 f are held along the longitudinal direction of theinner wall of this tubular base member 3 at specified distances fromeach other.

The functions of the optical fiber measuring module 60 according to thesixth embodiment are described. Since the three optical fiber cables 2d, 2 e, 2 f are held along the longitudinal direction of the inner wallof this tubular base member 3 at the specified distances from each otherto be three-dimensionally arranged in this optical fiber measuringmodule 60, state quantities of the structure 1 such as thethree-dimensional deformation and distortion thereof can be efficientlymeasured in a remote plate by a simple construction.

Similar to the optical fiber measuring module 50 of the fifthembodiment, the optical fiber measuring module 60 of the sixthembodiment has the effect that the elongation, lateral pressure, bendingforce and the like acting on the base member 3 can be analyzed byanalyzing the distortion pattern of the fiber cables 2 d, 2 e, 2 f asshown in FIG. 7B.

Next, a seventh embodiment of the present invention is described withreference to FIG. 9. FIG. 9 is a perspective view showing a constructionof an optical fiber measuring module 70 according to the seventhembodiment of the invention.

With reference to FIG. 9, in the optical fiber measuring module 70 ofthe seventh embodiment, optical fiber cables 2 d, 2 e, 2 f are spirallyheld on the inner wall of the tubular base member 3 in order to make theoptical fiber measuring module 70 difficult to break upon thedeformation of the base member 3 by making distortions acting in thelongitudinal directions of the optical fiber cables 2 d, 2 e, 2 f inresponse to a longitudinal deformation of the tubular base member 3relatively smaller.

Further, in an optical fiber measuring module 70, the base member 3 isformed with slits 8 for enhancing the flexibility of the base member 3in such a manner as to avoid the held optical fiber cables 2 d, 2 e, 2 fin order to make the base member 3 applicable to structures 1 of variousshapes such as the structure 1 of such as a shape as to have acurvature.

The functions of the optical fiber measuring module 70 according to theseventh embodiment are described. Since the optical fiber cables 2 d, 2e, 2 f are spirally held on the inner wall of the tubular base member 3in this optical fiber measuring module 70, distortions acting in thelongitudinal directions of the optical fiber cables 2 d, 2 e, 2 f inresponse to the longitudinal direction of the base member 3 can be maderelatively smaller. As a result, the optical fiber measuring module 70can be made more difficult to break upon the deformation of the basemember 3.

Further, since the slits 8 for enhancing the flexibility of the basemember 3 are so formed in the base member 3 as to avoid the held opticalfiber cables 2 d, 2 e, 2 f in the optical fiber measuring module 70,they restrict a maximum resilient bending curvature of the base member3. As a result, the optical fiber measuring module can be made highlysafe by preventing the leak of the light in light conducting paths ofthe optical fiber cables 2 d, 2 e, 2 f.

Next, an eighth embodiment of the present invention is described withreference to FIGS. 10 and 11. FIG. 10 is a perspective view showing aconstruction of the optical fiber measuring module 80 according to theeighth embodiment of the invention, and FIG. 11 is a section showing theaction of the optical fiber measuring module 80 according to the eighthembodiment of the invention.

With reference to FIG. 10, in the optical fiber measuring module 80 ofthe eighth embodiment, the base member 3 includes a strip-shaped flatportion 3 a and a wall portion 3 b standing substantially uprightsubstantially in the middle of the flat portion 3 a, two optical fibercables 2 d, 2 e are held along the longitudinal direction of the flatportion 3 a at a specified distance from each other, and another opticalfiber 2 f is held along the longitudinal direction of the wall portion 3b in order to enable measurements of state quantities of the structure 1such as the three-dimensional deformation and distortion thereof.Further, slits 8 for enhancing the flexibility of the base member 3 areso formed in the strip-shaped flat portion 3 a and the wall portion 3 bof the base member 3 as to avoid the held optical fiber cables 2 d, 2 e,2 f.

Here, the functions of the optical fiber measuring module 80 of theeighth embodiment are described. With reference to FIG. 11, in thisoptical fiber measuring module 80, a maximum bending angle is S/4d rad.and a minimum circle diameter is 2(S4+S5)d/S4 if intervals between theslits 8 are S5 and the width and height of the slits 8 are S4 and d.Thus, a light loss caused by an excessive bending can be avoided bydetermining the factors of the slits 8 such that the maximum bendingangle does not exceed a permissible bending angle of the optical fibercables 2.

As described above, in this optical fiber measuring module 80 of theeighth embodiment, the slits 8 for enhancing the flexibility of the basemember 3 are so formed in the base member 3 as to avoid the held opticalfiber cables 2 d, 2 e, 2 f and the deformations of the optical fibercables 2 d, 2 e, 2 f in response to an excessive deformation of thestructure 1 can be made not to exceed the permissible value. Thus, theoptical fiber measuring module 80 can be made highly versatile andapplicable in a wide range of structures 1 including those expected toexperience large deformations.

Next, a ninth embodiment of the present invention is described withreference to FIG. 12. FIG. 12 is a perspective view showing aconstruction of an optical fiber measuring module 90 according to theninth embodiment of the invention.

With reference to FIG. 12, in the optical fiber measuring module 90 ofthe ninth embodiment, the base member 3 is strip-shaped in order toenable state quantities of the structure such as the deformation anddistortion thereof to be efficiently measured in a remote place by asimple construction, and one optical fiber cable 2 is held along thelongitudinal direction of the base member 3. Further, slits 8 forenhancing the flexibility of the base member 3 is so formed in the basemember 3 as to avoid the held optical fiber cable 2 lest the deformationof the optical fiber cable 2 should exceed a permissible value.

The functions of the optical fiber measuring module 90 according to theninth embodiment are described. Since the base member 3 is formed withthe slits 8 for alleviating the elongation of the base member 3 in thisoptical fiber measuring module 90, the deformation of the optical fibercable 2 in response to an excessive deformation of the structure 1 onwhich the optical fiber measuring module 90 is laid can be made not toexceed the permissible value. As a result, the optical fiber measuringmodule 90 can be made highly versatile and applicable in a wide range ofstructures 1 including those expected to experience large deformations.

Next, a tenth embodiment of the present invention is described withreference to FIG. 13. FIG. 13 is a perspective view showing aconstruction of an optical fiber measuring module 100 according to thetenth embodiment of the invention.

With reference to FIG. 13, in the optical fiber measuring module 100 ofthe tenth embodiment, the optical fiber cable 2 is held on the basemember 3 in a wavy manner, notches 9 used to bend the base member 3 areformed at lateral ends of the base member 3 located on extensions oftangents to the optical fiber cable 2 extending from peaks of waves totroughs thereof, and the base member 3 is bent along these notches 9 andthe optical fiber cable 3.

The functions of the optical fiber measuring module 100 according to thetenth embodiment are described. In this optical fiber measuring module100, the base member 3 can be bent along the optical fiber cable 2 whilethe optical fiber cable 2 is only twisted at a bending positiondetermined by the notches 9. Thus, the optical fiber measuring module100 can be placed at a corner portion 11 of the structure 1.

Next, an eleventh embodiment of the present invention is described withreference to FIGS. 14 to 17. FIG. 14 is a perspective view showing aconstruction of an optical fiber measuring module 110 according to theeleventh embodiment of the invention; FIG. 15 is a perspective viewshowing a construction of a unit of the optical fiber measuring module110 according to the eleventh embodiment of the invention; FIG. 16 is aperspective view showing a construction of a polarizing ring 12 of theoptical fiber measuring module 110 according to the eleventh embodimentof the invention; and FIGS. 17A and 17B are side views showing aconstruction of a loading mechanism 14 for the polarizing ring 12,wherein FIG. 17A shows a state where the length of a discontinuousportion 15 is not changed by a loading member 16 and FIG. 17B shows astate where the length of the discontinuous portion 15 is changed by theloading member 16.

With reference to FIGS. 14 and 15, the optical fiber measuring module110 of the eleventh embodiment is provided with the base members 3having a standardized length and coupling portions 2 g of the opticalfiber 2 located at the opposite ends of these standardized base members3, and the coupling portions 2 d of the optical fiber cable 2 areoptically coupled to each other to successively connect the base members3, whereby the optical fiber measuring module 110 can deal withstructures 1 having different sizes.

Further, in the optical fiber measuring module 110 of the eleventhembodiment, the optical fiber cables 2 are looped to provide thepolarizing rings 12, which correct polarized states of signal lightspropagating in the optical fiber cables 2.

The polarizing ring 12 is formed by looping the optical fiber cable 2 ofa SM (single mode) and provided with a ring base member 13 for holdingthe optical fiber cable 2 forming the polarizing ring 12 and a loadingmechanism 14 capable of giving a distortion in a circumferentialdirection of the ring base member 13. The optical fiber cable 2 held inthe ring base member 13 is distorted to correct the distortion by givingthe distortion in the circumferential direction of the ring base member13 by means of this loading mechanism 14.

As shown in FIG. 17A, the loading mechanism 14 includes a discontinuousportion 15 formed in the ring base member 13, a loading member 16 heldin contact with the opposite ends of the ring base member 13 facing thediscontinuous portion 15, and a loading-member shaft 17 providedsubstantially in the center of the loading member 16 and rotatablysupporting the loading member 16. The length of the discontinuousportion 15 of the ring base member 13 is changed by turning the loadingmember 16 about the loading-member shaft 17 as shown in FIG. 17B,thereby changing the distortion to the ring base member 13.

With reference to FIGS. 14 to 17, the functions of the optical fibermeasuring module 110 of the eleventh embodiment are described. Thisoptical fiber measuring module 110 is provided with the base member 3having a standardized length and the coupling portions 2 g of theoptical fiber cable 2 provided at the opposite ends of each base member3. Since the coupling portions 2 d of the optical fiber cables 2 areoptically coupled to each other to successively connect the base members3, the optical fiber measuring module 110 can deal with differentlydimensioned structures 1, thereby being made more versatile.

Further, the optical fiber measuring module 110 of the eleventhembodiment can conduct a precise measurement since the polarized stateof the signal light propagating in the optical fiber cable 2 can becorrected by the polarizing ring 12 formed by looping the optical fibercable 2.

In the optical fiber measuring module 110 of the eleventh embodiment, adistortion is given in the circumferential direction of the ring basemember 13 by the loading mechanism 14 capable of giving the distortionin the circumferential direction of the ring base member 13 holding theoptical fiber cable forming the polarizing ring 12, whereby the opticalfiber cable 2 held in the ring base member 13 can be distorted tocorrect the distortion of the optical fiber measuring module. Thus, theoptical fiber measuring module 110 can conduct a more precisemeasurement.

Further, in the optical fiber measuring module 110 of the eleventhembodiment, the distortion of the optical fiber measuring module can beeasily corrected by a simple construction of changing the length of thediscontinuous portion 15 of the ring member 13 to change the distortionof the ring base member 13 by turning the loading member 16 in contactwith the opposite ends of the ring base member 13 facing thediscontinuous portion 15 of the loading mechanism 14 about theloading-member shaft 17 provided substantially in the center of theloading member 16.

The aforementioned embodiments are merely the illustrations of preferredspecific examples and the present invention is not limited thereto.

For example, the optical fiber cable 2 is not necessarily held on thebase member 3 in a straight, wavy or spiral manner as shown, and variousdesign changes can be made on the holding mode of the optical fibercable 2.

Further, the shape of the base member 3 is not necessarily restricted tothe strip shape, plate shape or tubular shape as shown, and variousdesign changes can be made thereon provided that the base member 3 has ashape capable of holding the optical fiber cable 2.

For example, FIGS. 18A and 18B show a modification of the base member 3,wherein FIG. 18A is a perspective view of this modification and FIG. 18Bis a graph of the distortion of the optical fiber cable 2 showing aneffect of this modification.

With reference to FIG. 18A, the base member 3 may be formed into twosemicylindrical members 3 c, 3 d for holding the optical fiber cable 2in the middle. Particularly, recesses and projections are formed atintervals S8 in one semicylindrical member 3 c shown in FIG. 18A,whereas recesses and projections are formed at intervals S9 and S10slightly different from the intervals S8 in the other semicylindricalmember 3 d. These two semicylindrical members 3 c, 3 d are engaged witheach other and the optical fiber cable 2 is adhered to the onesemicylindrical member 3 c. Thus, as shown in FIG. 18B, the opticalfiber cable 2 can be held while giving different distortions: distortionε3=(S9−S8)/S8 in areas engaged at the intervals S9 and distortionε4=(S10−S8)/S8 in areas engaged at the intervals S10, to the opticalfiber cable 2 along the longitudinal direction of the optical fibercable 2.

Further, the shape of the attachment member 4 is not necessarilyrestricted to the plate shape as shown, and various design changes canbe made thereon provided that the attachment member 4 is so shaped as tobe able to attach the base member 2 to the structure 1.

Furthermore, the attaching device 5 is not restricted to the adheringlayer 7 made of an adhesive or a welding agent or a combination of thebottomed locking groove 5 c formed in the structure 1 and the engagingprojection 5 d formed on the attachment member 4 and to be pressed intothe locking groove 5 c as shown. Various design changes can be made onthe attaching device 5.

Further, the shape of the slits 8 for enhancing the flexibility of thebase member 3 is not restricted to the shown one. Various design changescan be made thereon provided that the slits 8 are formed to avoid theheld optical fiber cable 2 and to enhance the flexibility of the basemember 3.

Furthermore, the shape of the loading mechanism 14 of the polarizingring 12 is not restricted to the shown one. Various design changes canbe made thereon provided that the loading mechanism 14 can correct thedistortion by giving a distortion in the circumferential direction ofthe ring base member 13 to distort the optical fiber cable 2 held in thering base member 13.

As described above, an optical fiber measuring module is to be laid on astructure for measuring at least one physical quantity from thedistortion and temperature of the structure. The optical fiber measuringmodule comprises an optical fiber cable including an optical fiber core,a cladding and a covering layer; a base member for holding the opticalfiber cable; and an attachment member for attaching the base member tothe structure.

The base member may be handled upon handling the optical fiber measuringmodule since the base member for holding the optical fiber cable isprovided. Thus, it is not necessary to directly handle the optical fibercable which requires a careful attention. Further, since the attachmentmember for attaching the base member to the structure is provided, theoptical fiber measuring module can be easily attached to the structurewithout influencing the optical fiber cable.

In a preferred mode, the optical fiber measuring module may furthercomprise an attaching device provided between the attachment member andthe structure for attaching the attachment member to the structure; anda locking device provided between the base member and the attachmentmember for locking the base member in the attachment member.

According to this preferred mode, since the attaching device forattaching the attachment member to the structure is provided between theattachment member and the structure, the attachment member can be easilyattached to the structure without working the structure and attachmentmember every time. Further, since the locking device for locking thebase member in the attachment member is provided between the base memberand the attachment member, the optical fiber measuring module can beeasily attached to the structure by successively locking the base memberin the attachment member with the attachment member attached to thestructure.

The attachment member may preferably include an adhering layer providedon the attachment member and made of an adhesive or a welding agent foradhering the attachment member and the structure.

According to this preferred mode, since the attachment member isattached to the structure by the attaching device including the adheringlayer provided on the attachment member and made of an adhesive or awelding agent for adhering the attachment member and the structure, theattachment member can be attached to the structure without damaging theoptical fiber cable.

The attaching device may preferably attach the attachment member to thestructure by pushing an engaging projection engageable with a bottomedlocking groove formed in the structure and narrower at an opening thanat a bottom portion into the locking groove via a resilient sheet madeof a resilient member.

According to this preferred mode, since the attachment member isattached to the structure by the attaching device of pushing theengaging projection provided on the attachment member into the bottomedlocking groove narrower at the opening than at the bottom portion viathe resilient sheet, the attachment member can be attached to thestructure without damaging the optical fiber cable.

The locking device may preferably lock the base member in the attachmentmember by the engagement of engaging portions provided at the basemember with locking portions provided at the attachment member.

According to this preferred mode, since the base member is locked in theattachment member by the locking device of locking the engaging portionsprovided at the base member in the locking portions provided at theattachment member, the base member can be attached to the attachmentmember in one operation without requiring any part for attachment suchas screws.

The locking device may preferably set an initial distortion of theoptical fiber cable for the correction of a zero of a measurement valueby differing intervals of the locking portions provided at theattachment member from those of the engaging portions provided at thebase member to give a distortion resulting from elongation orcontraction to the base member locked in the attachment member.

According to this preferred mode, since the distortion resulting fromelongation or contraction can be given to the base member locked in theattachment member by differing the intervals of the locking portionsprovided at the attachment member and those of the engaging projectionsprovided at the base member, the initial distortion of the optical fibercable can be set for the correction of the zero of the measurementvalue. As a result, a spatial position of the optical fiber measuringmodule can be displayed.

In another preferred mode, the base member may hold two or three opticalfiber cables at specified distances from each other, thereby enablingthe measurement of at least one state quantity from the elongation,bending and partial lateral pressure of the structure on which theoptical fiber measuring module is laid from measurement values ofdistortions of optical fiber cables and an increasing/decreasing patternof the measurement values.

According to this preferred mode, the base member holds the two or threeoptical fiber cables at specified distances from each other, whereby atleast one state quantity from the elongation, bending and partiallateral pressure of the structure on which the optical fiber measuringmodule is laid can be measured from the measurement values of thedistortions of the optical fiber cables and the increasing/decreasingpattern of the measurement values. Thus, the state quantities such asthe deformation and distortion of the structure can be efficientlymeasured in a remote place.

In still another preferred mode, the base member may be strip-shaped andhold two optical fiber cables along the longitudinal direction of thebase member at a specified distance form each other.

According to this preferred mode, since the two optical fiber cables areheld along the longitudinal direction of the strip-shaped base member atthe specified distance from each other, the state quantities such as theplanar deformation and distortion of the structure can be efficientlymeasured in a remote place by a simple construction.

In further another preferred mode, the base member may include astrip-shaped flat portion and a wall portion standing substantiallyupright substantially in the middle of the flat portion. Two opticalfiber cables are held along the longitudinal direction of the flatportion at a specified distance from each other, and another opticalfiber cable is held along the longitudinal direction of the wallportion.

According to this preferred mode, since the two optical fiber cables areheld along the longitudinal direction of the strip-shaped flat portionat the specified distance from each other and another optical fibercable is held along the longitudinal direction of the wall portionstanding substantially upright substantially in the middle of the flatportion, the state quantities such as the three-dimensional deformationand distortion of the structure can be efficiently measured in a remoteplace by a simple construction.

It may be preferable that the base member is formed to have a tubularshape, and three optical fiber cables are held along the longitudinaldirection of the inner wall of the tubular base member at specifieddistances from each other.

According to this preferred mode, since the three optical fiber cablesare held along the longitudinal direction of the inner wall of thetubular base member at the specified distances from each other, thestate quantities such as the three-dimensional deformation anddistortion of the structure can be efficiently measured in a remoteplace by a simple construction.

In still another preferred embodiment, the optical fiber cables may bespirally held on the inner wall of the tubular base member.

According to this preferred mode, since the optical fiber cables arespirally held on the inner wall of the tubular base member, distortionsacting in the longitudinal directions of the optical fiber cables inresponse to a longitudinal deformation of the base member can be maderelatively smaller. As a result, the optical fiber measuring module canbe made difficult to break upon the deformation of the base member.

In further another preferred embodiment, the base member may be formedwith slits for enhancing the flexibility of the base member in such amanner as to avoid the held optical fiber cable(s), and the opticalfiber measuring module can be so laid as not to exceed a permissibledistortion of the optical fiber cable(s) upon being handled.

According to this preferred mode, since the base member is formed withthe slits for enhancing the flexibility of the base member in such amanner as to avoid the held optical fiber cable(s) and the optical fibermeasuring module can be so laid as not to exceed the permissibledistortion of the optical fiber cable(s) upon being handled, the opticalfiber measuring module can be made more effective without deterioratingthe light transmission of the fiber.

In another preferred embodiment, the base member may be formed withslits for enhancing the flexibility of the base member in such a manneras to avoid the held optical fiber cable(s), whereby the distortion ofthe optical fiber cable(s) can be prevented from exceeding a permissiblevalue even in response to an excessive deformation of the structure onwhich the optical fiber measuring module is laid.

According to this preferred mode, the base member is formed with theslits for enhancing the flexibility of the base member in such a manneras to avoid the held optical fiber cable(s), whereby the distortion ofthe optical fiber cable(s) can be prevented from exceeding thepermissible value even in response to the excessive deformation of thestructure on which the optical fiber measuring module is laid. Thus, theoptical fiber measuring module can be made to have such a highversatility as to be applicable to structures expected to be largelydeformed.

In still another preferred embodiment, the base member may hold theoptical fiber cable in a wavy manner and be formed with notches used tobend the base member at its lateral ends located on extensions oftangents to the optical fiber cable extending from peaks of waves totroughs thereof, whereby the distortion of the optical fiber cableresulting from bending can be prevented from exceeding a permissibledistortion by bending the base member along the notches and the opticalfiber cable to cause the optical fiber cable to be only twisted.

According to this preferred mode, the base member holds the opticalfiber cable in a wavy manner and is formed with the notches used to bentthe base member at its lateral ends located on the extensions of thetangents to the optical fiber cable extending from the peaks of thewaves to the troughs thereof, whereby the distortion of the opticalfiber cable resulting from bending can be prevented from exceeding thepermissible distortion by bending the base member along the notches andthe optical fiber cable to cause the optical fiber cable to be onlytwisted. Thus, the optical fiber measuring module can be made to havesuch a high versatility as to be applicable to corner portions ofstructures.

In still another preferred embodiment, the optical fiber measuringmodule may comprise base members having a standardized length; andcoupling portions of the optical fiber cable provided at the oppositeends of each standardized base member, and the coupling portions of theoptical fiber cables are optically coupled to each other to successivelyconnect the base members, thereby enabling structures of different sizesto be handled.

According to this preferred mode, the optical fiber measuring modulecomprises the base members having the standardized length and thecoupling portions of the optical fiber cable provided at the oppositeends of each standardized base member, and the coupling portions of theoptical fiber cables are optically coupled to each other to successivelyconnect the base members, thereby enabling structures of different sizesto be handled. Thus, the optical fiber measuring module can be made tohave an even higher versatility.

In further another preferred embodiment, the optical fiber measuringmodule may further comprise a polarizing ring formed by looping theoptical fiber cable, and a polarized state of a signal light propagatingin the optical fiber cable is corrected by the polarizing ring.

According to this preferred mode, precise measurements can be made sincethe polarized state of the signal light propagating in the optical fibercable can be corrected by the polarizing ring formed by looping theoptical fiber cable.

In another preferred embodiment, the optical fiber measuring module mayfurther comprise a ring base member for holding the optical fiber cableforming the polarizing ring and a loading mechanism capable of giving adistortion in a circumferential direction of the ring base member, andthe optical fiber cable held by the ring base member is distorted tocorrect the distortion by giving the distortion in the circumferentialdirection of the ring base member by device of the loading mechanism.

According to this preferred mode, the distortion is given in thecircumferential direction of the ring base member by the loadingmechanism capable of giving the distortion in the circumferentialdirection of the ring base member holding the optical fiber cableforming the polarizing ring, thereby giving the distortion to theoptical fiber cable held by the ring base member to enable thecorrection of the distortion of the optical fiber measuring module.Thus, more precise measurement can be made.

In still another preferred embodiment, the loading mechanism may includea discontinuous portion provided in the ring base member, a loadingmember held in contact with the opposite ends of the ring base memberfacing the discontinuous portion, and a loading-member shaft providedsubstantially in the center of the loading member and rotatablysupporting the loading member, and the length of the discontinuousportion of the ring base member is changed by rotating the loadingmember about the loading-member shaft, thereby changing the distortionof the ring base member.

According to this preferred embodiment, the loading member held incontact with the opposite ends of the ring base member facing thediscontinuous portion is rotated about the loading-member shaft providedsubstantially in the center of the loading member, whereby the length ofthe discontinuous portion of the ring base member is changed to changethe distortion of the ring member. Thus, the distortion of the opticalfiber measuring module can be easily corrected by a simple construction.

As described above, the present invention has a remarkable effect ofproviding optical fiber measuring modules which can be easily attachedto and detached from structures without damaging the optical fiber coresrequired to be carefully handled.

It should be appreciated that various other design changes can be madewithout departing from the scope and spirit of the present invention.

1. An optical fiber measuring module to be laid on a structure formeasuring at least one physical quantity from the distortion andtemperature of the structure, comprising: an optical fiber cableincluding an optical fiber core, a cladding and a covering layer, a basemember for holding the optical fiber cable, and an attachment member forattaching the base member to the structure.
 2. An optical fibermeasuring module according to claim 1, further comprising: an attachingdevice provided between the attachment member and the structure forattaching the attachment member to the structure, and a locking deviceprovided between the base member and the attachment member for lockingthe base member in the attachment member.
 3. An optical fiber measuringmodule according to claim 2, wherein the attachment member includes anadhering layer provided on the attachment member and made of an adhesiveor a welding agent for adhering the attachment member and the structure.4. An optical fiber measuring module according to claim 2, wherein theattaching device attaches the attachment member to the structure bypushing an engaging projection engageable with a bottomed locking grooveformed in the structure and narrower at an opening than at a bottomportion into the locking groove via a resilient sheet made of aresilient member.
 5. An optical fiber measuring module according toclaims 2, wherein the locking device locks the base member in theattachment member by the engagement of engaging portions provided at thebase member with locking portions provided at the attachment member. 6.An optical fiber measuring module according to claim 5, wherein thelocking device sets an initial distortion of the optical fiber cable forthe correction of a zero of a measurement value by differing intervalsof the locking portions provided at the attachment member from those ofthe engaging portions provided at the base member to give a distortionresulting from elongation or contraction to the base member locked inthe attachment member.
 7. An optical fiber measuring module according toclaim 1, wherein the base member holds two or three optical fiber cablesat specified distances from each other, thereby enabling the measurementof at least one state quantity from the elongation, bending and partiallateral pressure of the structure on which the optical fiber measuringmodule is laid from measurement values of distortions of optical fibercables and an increasing/decreasing pattern of the measurement values.8. An optical fiber measuring module according to claim 1, wherein thebase member is strip-shaped and holds two optical fiber cables along thelongitudinal direction of the base member at a specified distance formeach other.
 9. An optical fiber measuring module according to claim 1,wherein the base member includes a strip-shaped flat portion and a wallportion standing substantially upright substantially in the middle ofthe flat portion, two optical fiber cables are held along thelongitudinal direction of the flat portion at a specified distance fromeach other, and another optical fiber cable is held along thelongitudinal direction of the wall portion.
 10. An optical fibermeasuring module according to claim 1, wherein the base member is formedto have a tubular shape, and three optical fiber cables are held alongthe longitudinal direction of the inner wall of the tubular base memberat specified distances from each other.
 11. An optical fiber measuringmodule according to claim 10, wherein the optical fiber cables arespirally held on the inner wall of the tubular base member.
 12. Anoptical fiber measuring module according to claim 1, wherein the basemember is formed with slits for enhancing the flexibility of the basemember in such a manner as to avoid the held optical fiber cable, andthe optical fiber measuring module can be so laid as not to exceed apermissible distortion of the optical fiber cable upon being handled.13. An optical fiber measuring module according to claim 1, wherein thebase member is formed with slits for enhancing the flexibility of thebase member in such a manner as to avoid the held optical fiber cable,whereby the distortion of the optical fiber cable can be prevented fromexceeding a permissible value even in response to an excessivedeformation of the structure on which the optical fiber measuring moduleis laid.
 14. An optical fiber measuring module according to claim 1,wherein the base member holds the optical fiber cable in a wavy mannerand is formed with notches used to bend the base member at its lateralends located on extensions of tangents to the optical fiber cableextending from peaks of waves to troughs thereof, whereby the distortionof the optical fiber cable resulting from bending can be prevented fromexceeding a permissible distortion by bending the base member along thenotches and the optical fiber cable to cause the optical fiber cable tobe only twisted.
 15. An optical fiber measuring module according toclaim 1, comprising: base members having a standardized length, andcoupling portions of the optical fiber cable provided at the oppositeends of each standardized base member, wherein the coupling portions ofthe optical fiber cables are optically coupled to each other tosuccessively connect the base members, thereby enabling structures ofdifferent sizes to be handled.
 16. An optical fiber measuring moduleaccording to claim 1, further comprising a polarizing ring formed bylooping the optical fiber cable, wherein a polarized state of a signallight propagating in the optical fiber cable is corrected by thepolarizing ring.
 17. An optical fiber measuring module according toclaim 16, further comprising: a ring base member for holding the opticalfiber cable forming the polarizing ring, and a loading mechanism capableof giving a distortion in a circumferential direction of the ring basemember, wherein the optical fiber cable held by the ring base member isdistorted to correct the distortion by giving the distortion in thecircumferential direction of the ring base member by means of theloading mechanism.
 18. An optical fiber measuring module according toclaim 17, wherein the loading mechanism includes: a discontinuousportion provided in the ring base member, a loading member which can beheld in contact with the opposite ends of the ring base member facingthe discontinuous portion, and a loading-member shaft providedsubstantially in the center of the loading member and rotatablysupporting the loading member, wherein the length of the discontinuousportion of the ring base member is changed by rotating the loadingmember about the loading-member shaft, thereby changing the distortionof the ring base member.